Mixtures A substance made up of 2 or more elements or compounds that are not chemically combined and can be separated 2 classifications 1. Homogeneous--> mixtures that are spread out evenly Ex. solutions 2. Heterogeneous--> mixtures are not spread out evenly Ex. Colloids and suspensions
KoolAid & Salt Water are examples of Homogeneous Mixtures Rice Krispy Bars, Paint & Pizza are examples of Heterogeneous Mixtures
What is a solution? A homogeneous mixture Ex. saltwater Made of 2 parts 1. Solute--> the substance that is considered to be dissolved (salt) 2. Solvent--> the substance in which the solute is dissolved (H 2 O)
How can you tell which is the solute and solvent? If 2 substances in the solution were in different phases, the one that changed phase is the solute (salt), and the substance that did not change phase is the solvent (H 2 O) If 2 substances are in the same phase originally, the substance in smaller amount is usually the solute (40 g alcohol), and the substance is greater quantity is usually the solvent (60 g H 2 O)
Which is the solute and solvent? 75% Cu and 25% Zn = brass alloy CO 2(g) and H 2 O (l) = carbonated beverage O 2(g) and air
Properties of Solutions Very small particle size:.01 nm-1 nm Do not separate upon standing Are transparent Cannot be separated by filtration Particles do not display the Tyndall Effect: the particles are too small to scatter light
Examples of Solutions Sucrose in H 2 O Food coloring in H 2 O Sodium Borate in H 2 O Carbonated Beverages Alloys (2 or more metals) H 2 O vapor in air
Colloids A heterogeneous mixture May or may not be transparent Medium particle size: 1 nm -1000 nm Do not separate upon standing Cannot be separated by filtration Particles display the Tyndall Effect: the particles are large enough to scatter light
Examples of Colloids Gelatin in H 2 O Milk Clouds
Suspensions A heterogeneous mixture Are not transparent Large particle size: over 1000 nm Particles settle out Can be separated by filtration May or may not display the Tyndall Effect
Examples of Suspensions Clay in H 2 O Cooking oil in H 2 O Spoiled milk
More about Solutions Solutions in which H 2 O is the solvent are called aqueous If H 2 O cannot act as the solvent, another liquid will Ex. CCl 4 & C 6 H 6 will act as fat solvents in the body Solutions in which alcohol is the solvent are called tinctures Ex: Betadine solution (I 2 crystals dissolved in CH 3 OH)
When 2 liquids dissolve in one another, they are said to be miscible When 2 liquids do not dissolve in one another, they are said to be immiscible Make sure to use these terms when describing the solubility of liquids in one another!!! Ex. Ethanol is miscible in H 2 O Ex. Oil is immiscible in H 2 O
Alloys are solutions made up of 2 or more metals Ex. Brass 70%Cu and 30% Zn Ex. Sterling silver (Cu & Silver) Ex. Amalgam--> an alloy made Hg and other metals that is used to make dental fillings
Why can we make so many aqueous solutions? H 2 O is known as the “universal solvent” because it can dissolve or be miscible with most polar substances ***Remember the “Like” dissolves “like” rule Polar substances have an unequal distribution of electron charge because of certain elements stronger or weaker desires to become a noble gas within the compound Ex. NaCl, C 12 H 22 O 11, ethanol (C 2 H 5 OH) Nonpolar substances have equal distribution of electron charge because all elements within the compound have the same desire to become a noble gas Ex. Kerosene (C x H y ), oil, ethane (C 2 H 6 ) - + - +
What makes something an electrolyte? An electrolyte is a substance that dissolves in H 2 O that conducts an electric current A substance must have ions (+ and - charged particles) to be an electrolyte Electrolytes may be classified as “strong” or “weak” depending on how many ions they produce in solution Examples include: sodium chloride (NaCl), potassium phosphate (K 3 PO 4 )
A nonelectrolyte is a substance that dissolves in H 2 O that does not conduct an electric current Nonelectrolytes are polar or nonpolar covalent compounds. Examples include: sucrose C 12 H 22 O 11 (polar), pure water H 2 O (polar), and iodine I 2 (nonpolar)
How can we increase the rate of dissolution? Rate of Dissolution--> the measure of how fast a substance dissolves Increase surface area of solute Increase the temperature Agitate the solution (stir) Increase the concentration of solvent so more particles come in contact with the solute
What is solubility? Solubility is the maximum amount of solute that can dissolve in a certain amount of solvent What main factors affect solubility? 1.Temperature 2.Pressure 3.Nature of the solute (polar vs. nonpolar)
Temperature as a factor As you increase the temperature of a solid or liquid, solubility increases By increasing the kinetic energy, the solvent particles are forced to come in contact with the solute particles more often and can take on more as a result As you increase the temperature of a gas, solubility decreases By increasing the kinetic energy, the gas particles are moving too quickly and leave the solution before they have a chance to collide with the solute (gases do not want to be put in a liquid solution!!!)
Pressure as a factor An increase or decrease in pressure of a solid or liquid in solution will have no affect on the solubility of that solution This is because there is little to no ability (or space between particles) to compress or expand solid or liquid An increase in pressure will increase the solubility of a gas This is because gas particles can be forced closer together (or farther apart) due to the large spacing between particles
What is saturation? When a solution has the maximum amount of solute dissolved in a certain amount of solvent at a given temperature, it is said to be saturated Saturated solutions are said to be in equilibrium rate of solute dissolving in solvent rate of solute crystallizing in solvent
Solubility Curve All data points on the line represent a saturated solution
Unsaturated versus Saturated Solutions? When a solution contains less solute than it could at a certain temperature, it is said to be unsaturated When a solution contains more solute than it normally could at a certain temperature, it is said to be supersaturated ***This is a dynamic condition that is very unstable
Solubility Curve All data points above the saturation line represent a supersaturated solution All data points below the saturation line represent an unsaturated solution
Solubility Curve for Gases Gases have too much kinetic energy and do not want to be dissolved in a liquid When temperature increases, solubility decreases for gases
More on gases… Henry’s Law--> the solubility of gases in a liquid is directly proportional to the partial pressure of that gas on the surface of that liquid Effervescence--> the rapid escape of gas from a liquid in which it dissolves
Dilute Versus Concentrated Solutions Dilute--> a low amount of solute is dissolved in a solvent Concentrated--> a high amount of solute is dissolved in a solvent These terms will not tell us whether a solution is saturated, unsaturated, or supersaturated The concentration of a solution can be found using the Molarity (M) and Molality (m) equations
Molarity M = moles of solute / L of solution Solution = solute + solvent Sample problem : How many grams of sodium chloride can be dissolved in 150. mL of water to make a.85 M solution?
What is the molarity of a solution made up of 150. mL of ethanol (C 2 H 5 OH) in 200. mL of water? D ethanol =.789 g/mL, D water = 1.00 g/mL
Molality m = moles of solute / kg of solvent Sample problem : How many grams of CCl 4 are needed to dissolve 28 g of I 2 to make a.050 m solution?
A solution containing 468 g of sucrose (C 12 H 22 O 11 ) per liter has a density of 1.18 g/mL. What is the molality of this solution?
How to make a dilute solution from a concentrated solution?
M 1 V 1 = M 2 V 2 M = molarity V = volume Sample problem: How much 12 M HCl do you need to make 500. mL of a 3.0 M HCl solution? How much water did you add to the concentrated 12 M solution? concentrateddilute
How much water would you need to make.850 L of 6.8 M sulfuric acid solution for 18 M solution?